Thermally-enhanced ball grid array package structure and method

ABSTRACT

A thermally-enhanced ball grid array package structure is provided that includes an integrated circuit chip, a heat spreader and a substrate. The integrated circuit chip has a specified surface area. The heat spreader is coupled to the integrated circuit chip. The substrate is coupled to the heat spreader. The substrate has a specified surface area. The heat spreader covers a specified portion of the surface area of the substrate that is greater than the surface area of the integrated circuit chip. The heat spreader is operable to dissipate heat from the integrated circuit chip over the specified portion of the surface area of the substrate.

TECHNICAL FIELD OF THE INVENTION

The present invention is directed in general to integrated circuits and,more specifically, to a thermally-enhanced grid array package structureand method.

BACKGROUND OF THE INVENTION

A conventional plastic integrated circuit package generally comprises alead frame or substrate, an integrated circuit die made of silicon, anda protective layer to protect the die and the electrical connectionsbetween the die and the substrate.

A popular packaging option for high performance integrated circuit diesis a ball grid array (BGA). Reasons for the popularity of the BGAinclude the absence of leads that can be bent, which greatly decreasesproblems resulting from improper handling and lack of planarity, and theability of BGAs to self-center, which reduces placement problems. Inaddition, by using a relatively dense array of metal balls forinput/output connections, BGAs provide a relatively small package sizeas compared with other typical packaging options.

However, because the substrate of a conventional integrated circuitpackage is made of fiberglass or another insulating material and theprotective layer is also made of an insulating material, heatdissipation from the integrated circuit die is limited. Thus, a BGApackage structure may be unable to meet thermal requirements in areassuch as disk drives, automotive applications, and the like.

SUMMARY OF THE INVENTION

In accordance with the present invention, a thermally-enhanced ball gridarray (BGA) package structure and method are provided that achieve lowerpackage thermal resistance. In particular, a heat spreader is providedbetween an integrated circuit die and a substrate of the BGA packagestructure in order to evenly distribute heat from the die over thesubstrate surface.

According to one embodiment of the present invention, athermally-enhanced BGA package structure is provided that includes anintegrated circuit chip, a heat spreader and a substrate. The integratedcircuit chip has a specified surface area. The heat spreader is coupledto the integrated circuit chip. The substrate is coupled to the heatspreader. The substrate has a specified surface area. The heat spreadercovers a specified portion of the surface area of the substrate that isgreater than the surface area of the integrated circuit chip. The heatspreader is operable to dissipate heat from the integrated circuit chipover the specified portion of the surface area of the substrate.

According to another embodiment of the present invention, a method forproviding a thermally-enhanced ball grid array package structurecomprising a plurality of metal balls is provided that includesproviding a substrate coupled to the metal balls. The substrate has aspecified surface area. A heat spreader is applied to the substrate. Anintegrated circuit chip is attached to the heat spreader. The integratedcircuit chip has a specified surface area. The heat spreader covers aspecified portion of the surface area of the substrate that is greaterthan the surface area of the integrated circuit chip. Heat is dissipatedfrom the integrated circuit chip over the specified portion of thesurface area of the substrate through the heat spreader.

Technical advantages of one or more embodiments of the present inventioninclude providing an improved BGA package structure. In a particularembodiment, a heat spreader is provided between the integrated circuitdie and the substrate of the BGA package structure, with the heatspreader extending over a large portion of the substrate. As a result,heat from the integrated circuit die is more evenly distributed over thesubstrate surface. Accordingly, the heat concentration on a circuitboard to which the BGA is coupled is reduced, improving the BGA packagestructure's thermal performance and allowing the structure to be used inhigher power dissipation applications.

Other technical advantages will be readily apparent to one skilled inthe art from the following figures, description, and claims.

Before undertaking the DETAILED DESCRIPTION OF THE INVENTION, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document: the terms “include” and “comprise,” aswell as derivatives thereof, mean inclusion without limitation; the term“or,” is inclusive, meaning and/or; the phrases “associated with” and“associated therewith,” as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like; and the term “controller”means any device, system or part thereof that controls at least oneoperation, such a device may be implemented in hardware, firmware orsoftware, or some combination of at least two of the same. It should benoted that the functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely.Definitions for certain words and phrases are provided throughout thispatent document, those of ordinary skill in the art should understandthat in many, if not most instances, such definitions apply to prior, aswell as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, wherein like referencenumerals represent like parts, in which:

FIG. 1 is a block diagram illustrating a ball grid array (BGA) packagestructure in accordance with one embodiment of the present invention;and

FIGS. 2A–E are block diagrams illustrating top views of selected layersof the BGA package structure of FIG. 1 in accordance with one embodimentof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 through 2E, discussed below, and the various embodiments used todescribe the principles of the present invention in this patent documentare by way of illustration only and should not be construed in any wayto limit the scope of the invention. Those skilled in the art willunderstand that the principles of the present invention may beimplemented for any suitably arranged grid array.

FIG. 1 is a block diagram illustrating a ball grid array (BGA) packagestructure 10 in accordance with one embodiment of the present invention.The structure 10 may comprise a plastic BGA or other suitable type ofBGA. In an alternative embodiment, the structure 10 may comprise a landgrid array. The structure 10 comprises an integrated circuit die, orchip, 12 coupled to a printed circuit board 14 through a plurality ofmetal balls 16, such as solder balls or balls comprising gold, tin orother suitable metal.

The structure 10 also comprises a substrate 20, a heat spreader 22, anda coupling layer 24. Openings in the heat spreader 22 allow bondingwires 30 to couple specified areas of the chip 12 to bonding fingers 32,which couple the specified areas of the chip 12 to the metal balls 16.In addition, the structure 10 comprises an encapsulation 40 over thechip 12, heat spreader 22, bonding wires 30 and bonding fingers 32.

The chip 12 may comprise a microprocessor, a microcontroller, a memorydevice, an application-specific integrated circuit, or any othersuitable integrated circuit device. The chip 12, which may comprisesilicon or other suitable material, is operable to function in anenvironment in which heat dissipation requirements are increased ascompared with typical chip applications, as well as in a typicalenvironment.

The printed circuit board 14 may comprise any suitable circuit board inwhich the chip 12 may be utilized. The metal balls 16 are operable tocouple the chip 12 to the printed circuit board 14. The substrate 20 maycomprise a fiberglass material or other suitable dielectric material.

According to one embodiment, the heat spreader 22 comprises copper.However, it will be understood that the heat spreader 22 may compriseany suitable thermally conductive material without departing from thescope of the present invention. The heat spreader 22 is attached to thesubstrate 20 with an adhesive layer (not shown in FIG. 1).

The heat spreader 22 covers a portion of the surface area of thesubstrate 20 that is greater than the surface area of the chip 12. For aparticular embodiment, the heat spreader 22 covers at least 75% of thesurface area of the substrate 20. However, it will be understood thatthe heat spreader 22 may cover any suitable portion of the surface areaof the substrate 20 that is greater than the surface area of the chip 12without departing from the scope of the present invention. Thus, theheat spreader 22 is operable to dissipate heat from the chip 12 evenlyacross the substrate 20, which conducts the heat to the printed circuitboard 14 through the metal balls 16.

The coupling layer 24 may comprise any suitable die attach materialoperable to couple the chip 12 to the heat spreader 22. For example, thecoupling layer 24 may comprise silver-filled epoxy or other suitableadhesive material.

The bonding wires 30 and bonding fingers 32 may comprise a goldcompound, such as Ni/Au, or other suitable electrically conductivematerial. The bonding wires 30 are operable to couple specified areas ofthe chip 12 to the bonding fingers 32. The bonding fingers 32 areoperable to couple the specified areas of the chip 12 to the printedcircuit board 14 through the metal balls 16.

The encapsulation 40 may comprise any suitable insulating material, suchas molding compound or the like. The encapsulation 40 is operable tocover the chip 12, heat spreader 22, bonding wires 30 and bondingfingers 32, thereby protecting the chip 12 and the electricalconnections between the chip 12 and the substrate 20.

FIGS. 2A–E are block diagrams illustrating top views of selected layersof the BGA package structure 10 in accordance with one embodiment of thepresent invention. FIGS. 2A–D illustrate four of the layers of thestructure 10, while FIG. 2E illustrates a top view of the four layers ofFIGS. 2A–D coupled together.

FIG. 2A illustrates the top of the substrate 20 in accordance with oneembodiment of the present invention. An adhesive layer 50 is illustratedin FIG. 2B. The adhesive layer 50 may comprise pre-preg or othersuitable adhesive material and is operable to couple the heat spreader22 to the top of the substrate 20. FIG. 2C illustrates the heat spreader22 in accordance with one embodiment of the present invention. FIG. 2Dillustrates the chip 12 in accordance with one embodiment of the presentinvention.

Thus, according to one embodiment, the chip 12 may be applied to theheat spreader 22, and the heat spreader 22 may be coupled to thesubstrate 20 through the adhesive layer 50. The resulting structure 60is illustrated in FIG. 2E.

In this embodiment, the chip 12 is applied to the heat spreader 22. Boththe heat spreader 22 and the adhesive layer 50 (not shown in FIG. 2E)comprise openings 64 to allow the chip 12 to be coupled to the substrate20 through bonding wires 30 and bonding fingers 32. In addition, inaccordance with the illustrated embodiment, the heat spreader 22 coversat least 75% of the surface area of the substrate 20.

In this way, heat from the chip 12 is evenly distributed over thesurface of the substrate 20. Accordingly, the heat concentration on theprinted circuit board 14 is reduced, improving the performance of theBGA package structure 10 and allowing the structure 10 to be used inhigher power dissipation applications.

Although the present invention has been described with severalembodiments, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present invention encompasssuch changes and modifications as fall within the scope of the appendedclaims.

1. A thermally-enhanced ball grid array package structure, comprising:an integrated circuit chip having a specified surface area; a heatspreader coupled to the integrated circuit chip; and a substrate coupledto the heat spreader, the substrate having a specified surface area, theheat spreader covering a specified portion of the surface area of thesubstrate that is greater than the surface area of the integratedcircuit chip, the heat spreader operable to evenly distribute heat fromthe integrated circuit chip over the specified portion of the surfacearea of the substrate, the heat spreader comprising a plurality ofopenings; a pre-formed adhesive layer adhering at least a portion of afirst surface of the heat spreader to a plurality of bonding fingers,and adhering at least a portion of a second surface of the heat spreaderto a surface of the substrate underlying the plurality of bondingfingers, the adhesive layer including a plurality of openings alignedwith the openings through the heat spreader, the plurality of bondingfingers each having a corresponding bonding wire, the bonding fingersand bonding wires operable to couple the integrated circuit chip to thesubstrate through the openings in the heat spreader and adhesive layer;an encapsulation operable to encapsulate at least a portion of theintegrated circuit chip, the heat spreader, the bonding wires, and thebonding fingers; and a plurality of metal balls coupled to thesubstrate, the metal balls operable to couple the integrated circuitchip to a printed circuit board, the metal balls further operable todistribute heat from the substrate to the printed circuit board.
 2. Thestructure of claim 1, the heat spreader comprising copper.
 3. Thestructure of claim 1, wherein the adhesive layer has a shapesubstantially identical to the heat spreader.
 4. The structure of claim3, the adhesive layer comprising pre-preg.
 5. The thermally-enhancedball grid array package structure according to claim 1, wherein the heatspreader covers at least 75% of the surface area of the first substratesurface.
 6. The structure of claim 1, wherein the specified portioncomprises at least 75% of the surface area of the substrate.
 7. Athermally-enhanced ball grid array package structure, comprising: asubstrate having a specified surface area; a heat spreader coupled tothe substrate, the heat spreader covering a specified portion of thesurface area of the substrate, the specified portion greater than asurface area of an integrated circuit chip operable to be coupled to thesubstrate through the heat spreader, the heat spreader operable toevenly distribute heat from the integrated circuit chip over thespecified portion of the surface area of the substrate, the heatspreader comprising a plurality of openings; a pre-formed adhesive layeradhering at least a portion of a first surface of the heat spreader to aplurality of bonding fingers, and adhering at least a portion of asecond surface of the heat spreader to a surface of the substrateunderlying the plurality of bonding fingers, the adhesive layerincluding a plurality of openings aligned with the openings through theheat spreader, the plurality of bonding fingers each having acorresponding bonding wire, the bonding fingers and bonding wiresoperable to couple the integrated circuit chip to the substrate throughthe openings in the heat spreader and adhesive layer; an encapsulationcomprising one or more insulating materials and operable to encapsulateat least a portion of the integrated circuit chip, the heat spreader,the bonding wires, and the bonding fingers; and a plurality of metalballs coupled to the substrate, the metal balls operable to couple theintegrated circuit chip to a printed circuit board, the metal ballsfurther operable to distribute heat from the substrate to the printedcircuit board.
 8. The structure of claim 7, the heat spreader comprisingcopper.
 9. The structure of claim 7, wherein the adhesive layer has ashape substantially identical to the heat spreader.
 10. The structure ofclaim 9, the adhesive layer comprising pre-preg.
 11. The structure ofclaim 7, wherein the specified portion comprises at least 75% of thesurface area of the substrate.
 12. A method for providing athermally-enhanced ball grid array package structure, comprising:providing a substrate having a specified surface area; applying a heatspreader to the substrate with an intervening pre-formed adhesive layeradhering at least a portion of a first surface of the heat spreader to aplurality of bonding fingers and adhering at least a portion of a secondsurface of the heat spreader to a surface of the substrate underlyingthe plurality of bonding fingers; applying an integrated circuit chip tothe heat spreader, the integrated circuit chip having a specifiedsurface area, the heat spreader covering a specified portion of thesurface area of the substrate, the specified portion greater than thesurface area of the integrated circuit chip, the heat spreader operableto evenly distribute heat from the integrated circuit chip over thespecified portion of the surface area of the substrate; coupling theintegrated circuit chip to the substrate through a plurality of openingsthrough the heat spreader and adhesive layer using a plurality ofbonding wires and the bonding fingers; encapsulating at least a portionof the integrated circuit chip, the heat spreader, the bonding wires,and the bonding fingers using an encapsulation, the encapsulationcomprising one or more insulating materials; and applying a plurality ofmetal balls to the substrate, the metal balls operable to couple theintegrated circuit chip to a printed circuit board, the metal ballsfurther operable to distribute heat from the substrate to the printedcircuit board.
 13. The method of claim 12, the heat spreader comprisingcopper.
 14. The method of claim 12, wherein the adhesive layer has ashape substantially identical to the heat spreader.
 15. The method ofclaim 14, the adhesive layer comprising pre-preg.
 16. The method ofclaim 12, wherein the specified portion comprises at least 75% of thesurface area of the substrate.
 17. A thermally-enhanced ball grid arraypackage structure, comprising: an integrated circuit chip coupled to afirst surface of an insulating substrate material on which are formedpatterned conductive traces; a heat spreader coupled to the firstsurface of the insulating substrate material, the heat spreadercomprising a plurality of openings and covering a surface area of thefirst surface of the insulating substrate material greater than asurface area of the integrated circuit chip; a pre-formed adhesive layeradhering at least a portion of a first surface of the heat spreader toat least portions of the patterned conductive traces and adhering atleast a portion of a second surface of the heat spreader to the firstsurface of the insulating substrate material, the adhesive layerincluding a plurality of openings aligned with the openings through theheat spreader; and a plurality of solder balls on a second surface ofthe insulating substrate material opposite the first surface, theplurality of solder balls electrically connected through the patternedconductive traces to the integrated circuit die.